U.S. patent application number 09/682319 was filed with the patent office on 2001-12-06 for pressure sensitive trip mechanism for a rotary breaker.
Invention is credited to Doma, Palani K., Douville, Gary.
Application Number | 20010048354 09/682319 |
Document ID | / |
Family ID | 24285153 |
Filed Date | 2001-12-06 |
United States Patent
Application |
20010048354 |
Kind Code |
A1 |
Douville, Gary ; et
al. |
December 6, 2001 |
Pressure sensitive trip mechanism for a rotary breaker
Abstract
A pressure sensitive trip mechanism for actuating a circuit
breaker operating mechanism to trip a circuit breaker includes a
trip lever and a trip bar. The trip lever is rotatable about a
first pivot. The trip bar is positioned proximate the trip lever.
The trip bar is arranged to rotate about a second pivot in response
to a predetermined level of pressurized gas created by separation
of the pair of electrical contacts, thereby urging the trip lever
to unlatch the circuit breaker operating mechanism. The pressure
sensitive trip mechanism provides for very fast tripping of the
circuit breaker in the event of a short circuit condition or an
overcurrent fault condition within any one on the circuit breaker
poles. In a multiple circuit breaker, the present invention
provides for protection against single-phasing.
Inventors: |
Douville, Gary; (East
Hartford, CT) ; Doma, Palani K.; (Bristol,
CT) |
Correspondence
Address: |
CANTOR COLBURN, LLP
55 GRIFFIN ROAD SOUTH
BLOOMFIELD
CT
06002
|
Family ID: |
24285153 |
Appl. No.: |
09/682319 |
Filed: |
August 20, 2001 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
|
|
09682319 |
Aug 20, 2001 |
|
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|
09571810 |
May 16, 2000 |
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Current U.S.
Class: |
335/172 |
Current CPC
Class: |
H01H 77/02 20130101;
H01H 2071/1036 20130101; H01H 1/2058 20130101; H01H 9/342 20130101;
H01H 71/1009 20130101; H01H 2077/025 20130101 |
Class at
Publication: |
335/172 |
International
Class: |
H01H 009/00 |
Claims
1. A circuit breaker assembly comprising: a first cassette: a first
contact mounted in said first cassette; a first movable contact arm
mounted in said first cassette; a second contact coupled to said
first movable contact arm; a pressure sensitive trip mechanism
including a trip bar rotatably coupled to an exterior portion of
said first cassette, a portion of said trip bar being positioned
proximate an opening in said first cassette; and an operating
mechanism in operable communication with said trip bar, wherein
said trip bar rotates to trip said operating mechanism in response
to a predetermined level of pressurized gas exhausting said first
cassette through said opening, said pressurized gas is created by
separation of said first contact and said second contact.
2. The circuit breaker assembly of claim 1 wherein said pressure
sensitive trip mechanism includes a trip lever extending between
said trip bar and said operating mechanism, said trip lever is
rotatably mounted about a first pivot located on an exterior
surface of said first cassette.
3. The circuit breaker assembly of claim 1 further comprising: a
trip finger disposed on said trip bar, said trip finger is
positioned proximate said first movable contact arm, said trip
finger being mechanically actuatable by said first movable contact
arm to rotate said trip bar.
4. The circuit breaker assembly of claim 1 further comprising: a
second cassette proximate said first cassette; a third contact
mounted in said second cassette; a second movable contact arm
having a fourth contact at one end; and wherein another portion of
said trip bar is positioned proximate an opening in said second
cassette.
5. A circuit breaker assembly comprising: a first cassette; a first
contact mounted in said first cassette; a first movable contact arm
mounted in said first cassette; a second contact coupled to said
first movable contact arm; an operating mechanism in operable
communication with said first movable contact arm; a pressure
sensitive trip mechanism including a first lever pivotally coupled
to an exterior portion of said first cassette, a first portion of
said first lever being positioned proximate an opening in said
first cassette, and a second portion of said first lever being
operably coupled to said operating mechanism; and wherein said
first lever rotates to trip said operating mechanism in response to
a predetermined level of pressurized gas exhausting said first
cassette through said opening, said pressurized gas is created by
separation of said first contact and said second contact.
6. The circuit breaker assembly of claim 5 wherein said pressure
sensitive trip mechanism includes a second lever extending between
said second portion of said first lever and said operating
mechanism, said second lever is rotatably mounted to an exterior
surface of said first cassette.
7. The circuit breaker assembly of claim 5 further comprising: a
trip finger disposed on said first end of said first lever, said
trip finger is positioned proximate said first movable contact arm,
said trip finger being mechanically actuatable by said first
movable contact arm to rotate said first lever.
8. The circuit breaker assembly of claim 5 further comprising: a
second cassette proximate said first cassette; a third contact
mounted in said second cassette; a second movable contact arm
having a fourth contact at one end; and wherein said first portion
of said first lever is positioned proximate an opening in said
second cassette.
9. A circuit breaker assembly comprising: a first cassette; a first
contact mounted in said first cassette; a first movable contact arm
rotatably mounted on an axle in said first cassette; a second
contact coupled to said first movable contact arm; an operating
mechanism in operable communication with said first movable contact
arm for rotating said first movable contact arm around said axle; a
pressure sensitive trip mechanism including a bar rotatably coupled
to an exterior portion of said first cassette, said bar extending
parallel to said axle, a first extension coupled to said bar, said
first extension being positioned proximate an opening in said first
cassette, and a protrusion extending from said bar, said protrusion
being operably coupled to said operating mechanism; and wherein
pressurized gas exhausting said first cassette through said opening
acts on said first extension to rotate said bar causing said
protrusion to trip said operating mechanism, said pressurized gas
is created by separation of said first contact and said second
contact.
10. The circuit breaker assembly of claim 9 wherein said pressure
sensitive trip mechanism includes a lever extending between said
protrusion and said operating mechanism, said lever is rotatably
mounted about a first pivot located on an exterior surface of said
first cassette.
11. The circuit breaker assembly of claim 9 further comprising: a
finger disposed on said first extension, said finger is positioned
proximate said first movable contact arm, said finger being
mechanically actuatable by said first movable contact arm to rotate
said bar.
12. The circuit breaker assembly of claim 9 further comprising: a
second cassette proximate said first cassette; a third contact
mounted in said second cassette; a second movable contact arm
having a fourth contact at one end; and wherein said pressure
sensitive trip mechanism further includes a second extension
coupled to said bar, said second extension being positioned
proximate an opening in said second cassette.
13. A circuit breaker comprising; a first cassette half-piece; a
second cassette half-piece coupled to said first cassette
half-piece, said first an second cassette half-pieces forming an
enclosed area therebetween; a first contact mounted in said
enclosed area; a movable contact arm mounted within said enclosed
area; a second contact coupled to said first movable contact arm;
an operating mechanism coupled to an exterior of at least one of
said first and second cassette half-pieces, said operating
mechanism operably coupled to said movable contact arm; a pressure
sensitive trip mechanism including a bar rotatable coupled to said
exterior of at least one of said first and second cassette
half-pieces, a first extension coupled to said bar, said first
extension being positioned proximate an opening in said first
cassette, said opening extending between said enclosed area and
said exterior of at least one of said first and second cassette
half-pieces, and a protrusion extending from said bar, said
protrusion being operably coupled to said operating mechanism; and
wherein pressurized gas exhausting said enclosed area through said
opening acts on said first extension to rotate said bar causing
said protrusion to trip said operating mechanism.
14. The circuit breaker of claim 13 wherein said pressure sensitive
trip mechanism includes a lever extending between said protrusion
and said operating mechanism, said lever is rotatably mounted to
said first cassette half-piece.
15. The circuit breaker of claim 13 further comprising: a finger
disposed on said first extension, said finger is positioned
proximate said first movable contact arm, said finger being
mechanically actuatable by said first movable contact arm to rotate
said bar.
Description
CROSS REFERENCE TO RELATED APPLICATIONS
[0001] This application is a continuation of U.S. patent
application Ser. No. 09/571,810, filed May 16, 2000, pending, which
is incorporated by reference herein in its entirety.
BACKGROUND OF INVENTION
[0002] The present invention relates generally to circuit breakers
and more particularly to a circuit breaker employing a pressure
sensitive trip mechanism for instantaneously unlatching the circuit
breaker operating mechanism in response to an overcurrent or short
circuit condition.
[0003] Circuit breakers are one of a variety of overcurrent
protective devices used for circuit protection and isolation. The
basic function of a circuit breaker is to provide electrical system
protection whenever an electrical abnormality occurs in any part of
the system. In a rotary contact circuit breaker, current enters the
system from a power source. The current passes through a line strap
to a fixed contact fixed on the strap and then to a moveable
contact. The moveable contact is fixedly attached to an arm, and
the arm is mounted to a rotor that in turn is rotatably mounted in
a cassette. As long as the fixed contact is in physical contact
with the moveable contact, the current passes from the fixed
contact to the moveable contact and out of the circuit breaker to
downstream electrical devices.
[0004] In the event of an extremely high overcurrent condition
(e.g. a short circuit), electro-magnetic forces are generated
between the fixed and moveable contacts. These electromagnetic
forces repel the movable contact away from the fixed contact.
Because the moveable contact is fixedly attached to a rotating arm,
the arm pivots and physically separates the fixed contact from the
moveable contact.
[0005] For a given model of circuit breaker, various types of trip
units may be used. For example, mounted within a circuit breaker
housing, a mechanical trip unit (e.g. thermal-magnetic or magnetic)
can be employed. Alternatively, an electronic trip unit can also be
employed that utilizes a current transformer. In order to trip the
circuit breaker, the selected trip unit must activate a circuit
breaker operating mechanism. Once activated, the circuit breaker
operating mechanism separates a pair of main contacts to stop the
flow of current in the protected circuit. Conventional trip units
act directly upon the circuit breaker operating mechanism to
activate the circuit breaker operating mechanism.
[0006] In all circuit breakers, the separation of the breaker
contacts due to a short circuit causes an electrical arc to form
between the separating contacts. The arc causes the formation of
relatively high-pressure gases as well as ionization of air
molecules within the circuit breaker. Exhaust ports are
conventionally employed to vent such gasses in a rotary contact
circuit breaker; each phase (pole) employs two pairs of contacts,
two contacts of which rotate about a common axis generally
perpendicular to the current path from the line side to the load
side of the circuit breaker. Each contact set in such an
arrangement requires an exhaust port to expel gasses.
[0007] During an overcurrent or short circuit condition, it is
desirable to trip the circuit breaker as quickly as possible in
order to minimize the energy that the circuit breaker must absorb.
For example, a very high level of arcing energy can develop when
interrupting short circuits. Relatively severe, high level, and
long lasting arcing can lead to excessive wear to the contacts as
well as the arc chutes. Furthermore, if the circuit breaker can
trip very quickly, higher interruption ratings can be achieved.
With higher interruption ratings, overall circuit performance is
improved. At the same time, any tripping system must also ensure
protection for the circuit breaker and the system in the event of a
single-phase condition, e.g. only one phase becomes overloaded. In
a multi-phase system, a single-phase condition exists when one pole
experiences a fault thereby blowing open and locking open the
contacts of that pole. The remaining poles do not experience the
fault and therefore their respective contacts remain closed. A
single-phase condition is never desirable in a multi-phase
system.
[0008] Therefore, it is desirable to provide a circuit breaker
tripping mechanism that will trip a circuit breaker very quickly
while ensuring protection of the circuit breaker and the electrical
system should a single-phase condition occur.
SUMMARY OF INVENTION
[0009] In the present invention, a pressure sensitive trip
mechanism for actuating a circuit breaker operating mechanism to
trip a circuit breaker includes a trip lever and a trip bar. The
trip lever is rotatable about a pivot and includes a first free end
and a second free end. The second free end is configured for
interacting with the latching mechanism. The trip bar is positioned
proximate said first free end of the trip lever. The trip bar is
arranged to rotate about a pivot in response to a predetermined
level of pressurized gas created by separation of the pair of
electrical contacts, thereby urging the second free end of the trip
lever to unlatch the circuit breaker operating mechanism.
[0010] In a further exemplary embodiment of the present invention,
a trip finger is employed with the pressure sensitive trip
mechanism to mechanically trip the circuit breaker. In this
embodiment of the present invention, at least one trip finger
protrudes radially outward from the trip bar. The trip finger is
configured for mechanically interacting with the movable contact
arm of the circuit breaker thereby urging the trip bar to rotate
about the pivot.
BRIEF DESCRIPTION OF DRAWINGS
[0011] FIG. 1 is a perspective view of a circuit breaker;
[0012] FIG. 2 is an exploded view of the circuit breaker of FIG.
1;
[0013] FIG. 3 is a perspective view of a circuit breaker cassette
assembly;
[0014] FIG. 4 is a perspective view of the pressure sensitive trip
mechanism, of the present invention, mounted onto a cassette;
[0015] FIG. 5 is a side view of the trip bar and trip lever of the
present invention, relative to a rotary contact assembly, showing
the contacts in a tripped position; and
[0016] FIG. 6 is a front end view of a center cassette and the trip
bar of the present invention.
DETAILED DESCRIPTION
[0017] Referring to FIG. 1, an embodiment of a molded case circuit
breaker 10 is generally shown. Circuit breakers of this type
generally an insulated case 16 having a cover 14 attached to a
mid-cover 12 coupled to a base 18. A handle 20 extending through
cover 14 gives the operator the ability to turn the circuit breaker
10 "on" to energize a protected circuit (shown on FIG. 3), turn the
circuit breaker "off" to disconnect the protected circuit (not
shown), or "reset"0 the circuit breaker after a fault (not shown).
A plurality of line-side contact and load-side straps 22, 24 also
extend through the case 16 for connecting the circuit breaker 10 to
the line and load conductors of the protected circuit. The circuit
breaker 10 in FIG. 1 shows a typical three phase configuration,
however, the present invention is not limited to this configuration
but may be applied to other configurations, such as one, two or
four phase circuit breakers.
[0018] Referring to FIG. 2, the handle 20 is attached to a circuit
breaker operating mechanism 26. The circuit breaker operating
mechanism 26 is coupled with a center cassette 28 and is connected
with outer cassettes 30 and 32 by drive pin 34. The cassettes 28,
30, and 32 along with the circuit breaker operating mechanism 26
are assembled into base 18 and retained therein by the mid-cover
12. The mid-cover 12 is connected to the base 18 by any convenient
means, such as screws 35, snap-fit (not shown) or adhesive bonding
(not shown). A cover 14 is attached to the mid-cover 12 by screws
36.
[0019] Referring to FIG. 3, a circuit breaker cassette assembly 38
is shown and comprises a rotary contact assembly, shown generally
at 40, in a first electrically-insulative cassette half-piece 42 of
center cassette 28 intermediate a line-side contact strap 22, and a
load-side contact strap 44. Line-side contact strap 22 is
electrically connectable to line-side wiring (not shown) in an
electrical distribution circuit, and load-side contact strap 44 is
electrically connectable to load-side wiring (not shown) via a lug
(not shown) or a mechanism such as a bimetallic element or current
sensor (not shown). Electrically insulative shields 46, 48 separate
load-side contact strap 44 and line-side contact strap 22 from the
associated arc chute assemblies 50, 52, respectively. Although only
a single circuit breaker cassette assembly 38 is shown, a separate
circuit breaker cassette assembly 38 is employed for each pole of a
multi-pole circuit breaker and operated in a manner similar to that
of circuit breaker cassette assembly 38.
[0020] Electrical transport through rotary contact assembly 40 of
circuit breaker cassette assembly 38 occurs from line-side contact
strap 22 to an associated first fixed contact 54, through first and
second movable contacts 56, 58 secured to the ends of a movable
contact arm, shown generally at 62, and to an associated second
fixed contact 60 on load-side contact strap 44. Movable contact arm
62 is pivotally arranged between two halves of a rotor 64 and moves
in conjunction with rotor 64 upon manual articulation of rotor 64.
Rotor 64 is rotatably positioned on a rotor pivot axle 102 (shown
below with reference to FIG. 5), the ends of which are supported by
inner parallel walls of first electrically-insulative cassette
half-piece 42.
[0021] The arc chute assemblies 50, 52 are positioned in the first
electrically insulative cassette half piece 42 adjacent the
respective pairs of first fixed and first moveable contacts 54, 56
and second fixed and second moveable contacts 60, 58. The first and
second movable contacts 56, 58 and moveable contact arm 62 move
through a passageway provided by the arc chute assemblies 50, 52 in
order to engage and disengage from the respective first and second
fixed contacts 54, 60. Each arc chute assembly 50, 52 is adapted to
interrupt and extinguish the arc which forms when the circuit
breaker 10 is tripped and the first and second moveable contacts
56, 58 are suddenly separated from the first and second fixed
contacts 54, 60.
[0022] Referring back to FIG. 2, it is understood circuit breaker
cassette assemblies 116, 118, that include cassettes 30, 32,
respectively, are similarly constructed to circuit breaker cassette
assembly 38 including rotary contact assembly 40 described
herein.
[0023] Referring to FIG. 4, a pressure sensitive trip mechanism
(unit) 66 is shown mounted onto a second electrically cassette
insulative half-piece 72. Center cassette 28 is formed by the
mating of electrically insulative cassette half-piece 72 with first
electrically insualtive cassette half-piece 42. The pressure
sensitive trip mechanism 66 comprises a trip bar 68 and a trip
lever 70. Trip bar 68 has a base section 80. Trip lever 70
comprises a first section 106 and a second section 108 and is
rotatably mounted about a pivot 74 located on an exterior surface
of center cassette 28 . First section 1 06 of trip lever 70 extends
in a generally horizontal direction adjacent the second
electrically insulative cassette half-piece 72 towards the center
of the center cassette 28. Second section 108 of trip lever 70
extends in a generally vertical direction adjacent to the second
electrically insulative cassette half-piece 72. A circuit breaker
operating mechanism 26 includes a latch assembly 78. Latch assembly
78 is actuatable by trip lever 70. The trip lever 70 is actuatable
by the trip bar 68. The trip bar 68 is preferably molded of a high
strength, high temperature thermoplastic. The trip lever 70 is
preferably stamped from steel, but can also be molded of high
strength plastic.
[0024] A bearing member 104 having a bearing surface 110 is
preferably integrally molded into the base 18 of the circuit
breaker 10 and has generally a flattened and thin structure.
Bearing surface 110 is positioned proximate to the bottom surface
of base section 80 of the trip bar 68 and is molded and shaped to
support the trip bar 68. A bend 119 is formed proximate to the base
section 80. Bearing member 104 provides structural support to the
trip bar 68 when the trip bar 68 is subjected to the high pressure
forces of the arc gases.
[0025] Referring to FIG. 5, the pressure sensitive trip mechanism
66 will be described in further detail. The pressure sensitive trip
mechanism 66 is shown as it would be positioned relative to contact
arm 62 of the rotary contact assembly 40. Rotary contact assembly
40 is shown in an "off" position.
[0026] Base section 80 of trip bar 68 comprises a at least one
extension 82 extending from the base section 80 and a protrusion 84
extending outward, preferably perpendicularly, from base section
80. Trip bar 68 is rotatable mounted about a pivot 86 located on
the exterior surface of the second electrically insulative cassette
half-piece 72 (FIG. 2). Preferably, pivot 86 is a first pivot pin
(not shown) and most preferably, first pivot pin is made of metal.
Pivot 86 is located on protrusion 84 and arranged for insertion
into a corresponding opening (not shown) located within the
exterior surface of the second electrically insulative cassette
half-piece 72. The extension 82 of trip bar 68 is inserted through
a corresponding opening 88 located generally in the lower section
of the center cassette 28 (FIG. 1). Opening 88 is located proximate
to the arc chute 50. Thus, extension 82, when inserted inside the
center cassette 28, is in gaseous communication with the arc chute
50. Preferably, base section 80 is generally flat and elongated in
order to accommodate positioning proximate to cassettes 28, 30,
32.
[0027] Trip lever 70 is rotatably mounted about a pivot 74 located
on the exterior surface of the second electrically insulative
cassette half-piece 72 (FIG. 2). Trip lever 70 includes a free end
92 of first section 1 06. Free end 92 is proximate to protrusion
84. Trip lever 70 also includes a free end 94. Free end 94 is
generally U-shaped so that movement of trip lever 70 in the
clockwise direction moves trip arm 96 in a direction to unlatch
latching mechanism 78.
[0028] For a multi-pole circuit breaker, each cassette 28, 30, 32
would have corresponding openings 88 located proximate to the
respective arc chutes 50 in order that the extensions 82 (shown in
phantom and solid lines in FIG. 4) extending from the base section
80 of trip bar 68 may be inserted through all cassettes being
utilized.
[0029] Referring back to FIGS. 3, 4 and 5, the movement of the
pressure sensitive trip mechanism 66 will now be detailed.
[0030] Under high-level short circuit or overcurrent faults, the
contact arm 62 is opened due to the magnetic forces at the fixed
and moveable contacts 54, 56, 58, 60. As the contact arm 62 is
opened and the moveable contacts 56, 58 are separated from the
fixed contacts 54, 60 a plasma arc is formed between the fixed and
moveable contacts 54, 56, 58, 60. This arc generates arc gases of
relatively high pressure within the center cassette 28.
[0031] Generally, the level of pressure created in the center
cassette 28 is proportional to the current and voltage levels of
the fault. Once the pressure inside the arc chute 50 reaches a
predetermined level that is consistent with the desired overcurrent
or short circuit overcurrent level for which a trip of the circuit
breaker 10 is desired, the extension 82 of trip bar 68 will rotate
counterclockwise about pivot 86 in response to the force exerted on
it by the increased pressure. The rotation of trip bar 68 will
cause radial protrusion 84 to make contact with, and apply a force
against, free end 92 of trip lever 70. The trip lever 70, in
reaction to the movement of trip bar 68, will rotate clockwise
about pivot 74. The free end 94 of trip lever 70 then makes contact
with the trip arm 96 of the latch assembly 78. Latch assembly 78
unlatches the circuit breaker operating mechanism 26 causing all
phases of the circuit breaker 1 0 to trip in response to the short
circuit or overcurrent fault condition.
[0032] Incidentally, it will be appreciated that the pressure
sensitive trip mechanism 66 can be arranged for use in a circuit
breaker having a plurality of cassettes 28, 30, 32 as shown in FIG.
1. Each pole of a particular circuit breaker utilizes one extension
82 located along trip bar 68. Each respective extension 82
extending from the trip bar 68 will react to the pressure created
within the corresponding cassette 28, 30, 32. In this way, the trip
lever 70 which is located proximate to the extension 82 of the trip
bar 68, as well as the trip bar 68, responds to a fault condition
in any pole of the circuit breaker 1 0. When a high level short
circuit or overcurrent fault occurs, the most loaded pole will trip
due to the pressure increase in the respective cassette 28, 30, 32.
In this way, each pole employs the trip bar 68 and the trip lever
70. A trip of one pole moves the latch assembly 78 thereby
unlatching the circuit breaker operating mechanism 26. Once the
circuit breaker operating mechanism 26 is unlatched, all contacts
associated with the poles of the circuit breaker are opened by the
circuit breaker operating mechanism 26 and the flow of electrical
current through the circuit breaker is stopped.
[0033] Referring to FIG. 5, in a further exemplary embodiment of
the present invention, a trip finger 100 is employed with the trip
bar 68 and trip lever 70 to mechanically trip the circuit breaker
10. In this embodiment of the present invention, at least one trip
finger 100 protrudes outward from the trip bar 68, preferably in
the same general direction as the protrusion 84. Trip finger 100 is
located proximate to contact arm 62 on the load side of the
cassette assembly 38.
[0034] Referring to FIGS. 2, 3 and 5, the manner in which the trip
finger 100 operates relative to the rotary contact assembly 40 in
order to mechanically trip the circuit breaker 10 will be
detailed.
[0035] Under high-level short circuit or overcurrent faults, the
contact arm 62 is opened due to the magnetic forces at the fixed
and moveable contacts 54, 56, 58, 60. As the contact arm 62 is
opened and the moveable contacts 54, 60 are separated from the
fixed contacts 56, 58, the contact arm 62 rotates counterclockwise
about rotor axle pivot 102. The rotation of the contact arm 62
causes the contact arm 62 to make contact with trip finger 100
located on trip bar 68. Trip bar 68 will then rotate
counterclockwise about pivot 86 in response to the force exerted on
the trip finger 100. The rotation of trip bar 68 will cause
protrusion 84 to make contact with, and apply force against, free
end 92 of trip lever 70. The trip lever 70, in reaction to the
movement of trip bar 68, will rotate clockwise about pivot 74. The
free end 94 of trip lever 70 then makes contact with the trip arm
96 of the latch assembly 78. Latch assembly 78 unlatches the
circuit breaker operating mechanism 26 causing all phases of the
circuit breaker to trip in response to the short circuit or
overcurrent fault condition.
[0036] Referring to FIG. 6, the line-side front end view of the
center cassette 28 relative to the trip bar 68 is shown. It will be
appreciated that in a multi-pole circuit breaker, the number of
trip fingers 100 utilized on the trip bar 68 will correspond to the
number of poles for a particular circuit breaker. Each pole or
phase of the circuit breaker utilizes one trip finger 100 located
along trip bar 68. For example, and referring to the three pole
circuit breaker 10 shown in FIG. 2, trip bar 68 would have three
extensions 82 and three trip fingers 100. In this way, each contact
arm 62 (FIG. 3) employed in a multi-pole circuit breaker
individually acts upon the respective trip finger 100 located on
the base section 86 of trip bar 68. Each respective trip finger 100
will be located proximate to the corresponding contact arm 62. When
a high level short circuit or overcurrent fault occurs, the most
loaded pole will trip causing the respective contact arm 62 to blow
open and make contact with the respective trip finger 100. In this
way, each pole employs the base section 80 (FIG. 5) and protrusion
84 of the trip bar 68 as well as the trip lever 70 (FIG. 5). A trip
of one pole moves the latch assembly 78 (FIG. 5) thereby unlatching
the circuit breaker operating mechanism 26 (FIG. 5). Once the
circuit breaker operating mechanism 26 is unlatched, all contacts
associated with the poles of the circuit breaker open and the flow
of electrical current through the circuit breaker is stopped.
[0037] Referring to FIGS. 2, 3 and 5, it is further noted and
within the scope of the invention that in the multi-pole circuit
breaker 10, a second pivot pin 98 or the first pivot pin (not
shown) may be utilized on protrusion 84 of trip bar 68 to fit into
a corresponding opening (not shown) in the exterior surface of the
outer cassette 30. Also, a second protrusion 114 may extend outward
from base section 80 and positioned proximate the center cassette
28 and the third cassette 32. Second protrusion 114 may utilize a
third pivot pin (not shown) for insertion into a corresponding
opening (not shown) in the exterior surface of first
electrically-insulative cassette half-piece 42 of center cassette
Z8. Second protrusion 114 may also utilize a fourth pivot pin (not
shown) for insertion into a corresponding opening (not shown) in
the exterior surface of outer cassette 32.
[0038] As described herein, the pressure sensitive trip mechanism
66 for actuating a circuit breaker operating mechanism to trip a
circuit breaker includes a trip lever 70 and a trip bar 68 and is
readily adaptable to a variety of circuit breakers. The pressure
sensitive trip mechanism 66 provides for very fast tripping of the
circuit breaker 10 in the event of a short circuit condition or an
overcurrent fault condition within any one of the circuit breaker
poles. Fast response time to trip the circuit breaker 10 is
achieved due to the close proximity of the trip bar 68 and
extensions 82 to the source of the high pressure generated within
the cassettes 28, 30, 32. Thus, the pressure sensitive trip
mechanism 66 will cause the circuit breaker to trip should any one
phase in a multi-phase circuit breaker blow open before the trip
unit (e.g. mechanical or electronic) can react and trip the circuit
breaker. Fast tripping during a short circuit condition protects
the fixed and movable contacts 54, 56, 58, 60 and arc chutes 50, 52
from excessive wear due to extended exposure to high arcing energy.
Finally, bearing member 104 provides structural support for the
trip bar 68 and ensures that the high pressure force acting on the
trip bar 68 is translated into a rotational force that rotates the
trip bar 68.
[0039] While this invention has been described with reference to a
preferred embodiment, it will be understood by those skilled in the
art that various changes may be made and equivalents may be
substituted for elements thereof without departing from the scope
of the invention. In addition, many modifications may be made to
adapt a particular situation or material to the teachings of the
invention without departing from the essential scope thereof.
Therefore, it is intended that the invention not be limited to the
particular embodiment disclosed as the best mode contemplated for
carrying out this invention, but that the invention will include
all embodiments falling within the scope of the appended
claims.
* * * * *